What is the pp film on the shoes?

Polypropylene film. Polypropylene is a common plastic material, which has the characteristics of light weight, flexibility, wear resistance and waterproof, so it is widely used in footwear manufacturing. As a protective layer of shoes, PP film covers the vamp or sole to protect shoes from damage or pollution during manufacture, storage and transportation. Can prevent dust, moisture, dirt and other substances from contacting the shoes and keep the shoes clean and tidy.